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bpo-46606: Reduce stack usage of getgroups and setgroups (GH-31073)

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NGROUPS_MAX was 32 before Linux 2.6.4 but 65536 since Linux 2.6.4.
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Inada Naoki 2022-02-22 11:59:27 +09:00 • committed by GitHub
parent 4140bcb1cd
commit 74127b89a8
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1 changed files with 23 additions and 56 deletions
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79
Modules/posixmodule.c
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@ -7623,21 +7623,15 @@ static PyObject *
os_getgroups_impl(PyObject *module) os_getgroups_impl(PyObject *module)
/*[clinic end generated code: output=42b0c17758561b56 input=d3f109412e6a155c]*/ /*[clinic end generated code: output=42b0c17758561b56 input=d3f109412e6a155c]*/
{ {
PyObject *result = NULL;
gid_t grouplist[MAX_GROUPS];
/* On MacOSX getgroups(2) can return more than MAX_GROUPS results /* On MacOSX getgroups(2) can return more than MAX_GROUPS results
* This is a helper variable to store the intermediate result when * This is a helper variable to store the intermediate result when
* that happens. * that happens.
* *
* To keep the code readable the OSX behaviour is unconditional, * See bpo-7900.
* according to the POSIX spec this should be safe on all unix-y
* systems.
*/ */
gid_t* alt_grouplist = grouplist; gid_t *grouplist = NULL;
int n; int n;
#ifdef __APPLE__
/* Issue #17557: As of OS X 10.8, getgroups(2) no longer raises EINVAL if /* Issue #17557: As of OS X 10.8, getgroups(2) no longer raises EINVAL if
* there are more groups than can fit in grouplist. Therefore, on OS X * there are more groups than can fit in grouplist. Therefore, on OS X
* always first call getgroups with length 0 to get the actual number * always first call getgroups with length 0 to get the actual number
@ -7646,56 +7640,25 @@ os_getgroups_impl(PyObject *module)
n = getgroups(0, NULL); n = getgroups(0, NULL);
if (n < 0) { if (n < 0) {
return posix_error(); return posix_error();
} else if (n <= MAX_GROUPS) {
/* groups will fit in existing array */
alt_grouplist = grouplist;
} else { } else {
alt_grouplist = PyMem_New(gid_t, n); n++; // Avoid malloc(0)
if (alt_grouplist == NULL) { grouplist = PyMem_New(gid_t, n+1);
if (grouplist == NULL) {
return PyErr_NoMemory(); return PyErr_NoMemory();
} }
} }
n = getgroups(n, alt_grouplist); n = getgroups(n, grouplist);
if (n == -1) { if (n == -1) {
if (alt_grouplist != grouplist) { PyMem_Free(grouplist);
PyMem_Free(alt_grouplist);
}
return posix_error(); return posix_error();
} }
#else
n = getgroups(MAX_GROUPS, grouplist);
if (n < 0) {
if (errno == EINVAL) {
n = getgroups(0, NULL);
if (n == -1) {
return posix_error();
}
if (n == 0) {
/* Avoid malloc(0) */
alt_grouplist = grouplist;
} else {
alt_grouplist = PyMem_New(gid_t, n);
if (alt_grouplist == NULL) {
return PyErr_NoMemory();
}
n = getgroups(n, alt_grouplist);
if (n == -1) {
PyMem_Free(alt_grouplist);
return posix_error();
}
}
} else {
return posix_error();
}
}
#endif
result = PyList_New(n); PyObject *result = PyList_New(n);
if (result != NULL) { if (result != NULL) {
int i; int i;
for (i = 0; i < n; ++i) { for (i = 0; i < n; ++i) {
PyObject *o = _PyLong_FromGid(alt_grouplist[i]); PyObject *o = _PyLong_FromGid(grouplist[i]);
if (o == NULL) { if (o == NULL) {
Py_DECREF(result); Py_DECREF(result);
result = NULL; result = NULL;
@ -7705,9 +7668,7 @@ os_getgroups_impl(PyObject *module)
} }
} }
if (alt_grouplist != grouplist) { PyMem_Free(grouplist);
PyMem_Free(alt_grouplist);
}
return result; return result;
} }
@ -8212,14 +8173,11 @@ static PyObject *
os_setgroups(PyObject *module, PyObject *groups) os_setgroups(PyObject *module, PyObject *groups)
/*[clinic end generated code: output=3fcb32aad58c5ecd input=fa742ca3daf85a7e]*/ /*[clinic end generated code: output=3fcb32aad58c5ecd input=fa742ca3daf85a7e]*/
{ {
Py_ssize_t i, len;
gid_t grouplist[MAX_GROUPS];
if (!PySequence_Check(groups)) { if (!PySequence_Check(groups)) {
PyErr_SetString(PyExc_TypeError, "setgroups argument must be a sequence"); PyErr_SetString(PyExc_TypeError, "setgroups argument must be a sequence");
return NULL; return NULL;
} }
len = PySequence_Size(groups); Py_ssize_t len = PySequence_Size(groups);
if (len < 0) { if (len < 0) {
return NULL; return NULL;
} }
@ -8227,27 +8185,36 @@ os_setgroups(PyObject *module, PyObject *groups)
PyErr_SetString(PyExc_ValueError, "too many groups"); PyErr_SetString(PyExc_ValueError, "too many groups");
return NULL; return NULL;
} }
for(i = 0; i < len; i++) {
gid_t *grouplist = PyMem_New(gid_t, len+1); // Avoid malloc(0)
for (Py_ssize_t i = 0; i < len; i++) {
PyObject *elem; PyObject *elem;
elem = PySequence_GetItem(groups, i); elem = PySequence_GetItem(groups, i);
if (!elem) if (!elem) {
PyMem_Free(grouplist);
return NULL; return NULL;
}
if (!PyLong_Check(elem)) { if (!PyLong_Check(elem)) {
PyErr_SetString(PyExc_TypeError, PyErr_SetString(PyExc_TypeError,
"groups must be integers"); "groups must be integers");
Py_DECREF(elem); Py_DECREF(elem);
PyMem_Free(grouplist);
return NULL; return NULL;
} else { } else {
if (!_Py_Gid_Converter(elem, &grouplist[i])) { if (!_Py_Gid_Converter(elem, &grouplist[i])) {
Py_DECREF(elem); Py_DECREF(elem);
PyMem_Free(grouplist);
return NULL; return NULL;
} }
} }
Py_DECREF(elem); Py_DECREF(elem);
} }
if (setgroups(len, grouplist) < 0) if (setgroups(len, grouplist) < 0) {
PyMem_Free(grouplist);
return posix_error(); return posix_error();
}
PyMem_Free(grouplist);
Py_RETURN_NONE; Py_RETURN_NONE;
} }
#endif /* HAVE_SETGROUPS */ #endif /* HAVE_SETGROUPS */